Conventionally, as an electric heater structure (heating device) having a configuration in which a helically-wound, coiled electric wire (heating coil) is supported by an insulating material, one in which a kneaded product prepared by adding an inorganic binder to ceramic fibers or the like and by adjusting them is formed in a plate-like shape to allow it to serve as a support member and a heating coil is attached thereto is known, for example (Patent Document 1, for example).
On the other hand, recently, a problem caused by inhalation of inorganic fibers by a human body and invasion of the inhaled fibers to the lung has been pointed out. Under such circumstances, bio-soluble inorganic fibers that do not or hardly cause problems even when inhaled by a human body have been developed (Patent Document 2, for example).